ci: make npm install explicit for jobs that need it

.gitlab-ci.yml

@@ -10,12 +10,10 @@ stages:
   - test
   - publish
 
-before_script:
-  - npm install
-
 build:
   stage: build
   script:
+    - npm install
     - npm run build
   artifacts:
     paths:
@@ -26,6 +24,7 @@ build:
 test:
   stage: test
   script:
+    - npm install
     - npm test
   tags:
     - docker